I'm very impressed with this book overall. The list of spells (derived from the previous Grimoire and other supplements) is pretty much comprehensive. That is, if you're running a GURPS game and want to add magic, this is pretty much the only book you need. (Add Thaumatology if you want to create magic SYSTEMS, but that's another review for another time.) The spells are well-balanced, and the discussion of magic systems (and items) is very well-laid out. For example, they give you a pricing formula for making magic items... but then show you how they derived their numbers. This is priceless for people adding magic to non-medieval settings (Victorian or modern, for example). The spells themselves are relevant to everything from ancients to medieval to victorian to modern to futuristic settings.
A couple issues. First, I'm not sure they completely thought through all the prerequisite chains. In some cases, you have long chains of prerequisites for flavorful but fairly mediocre spells, or major potential flavor issues (high-tech spells that require that you go deep in Necromancy, for example). In the book's defense, it also gives you guidelines for changing those systems. The spells themselves aren't very flavorful... but this is by design, and I think it was the right decision. The book points out ways in which a campaign-appropriate flavor can be added. The artwork is awful.
More seriously, the decision to order the spells by their prerequisites was a bad one. For the player thumbing through the book looking for spells to buy, the ordering does make some sense, but when you go to look up a spell as a reference, you're totally lost. In any event, spells often have multiple prereqs and so the book doesn't even follow its own logic. Better to have gone by spell college, and then within each college alphabetically. SJ Games offers a free PDF with a graphical tree of each spell and its prerequisites in any event, which again helps with character creation, but doesn't help at all as an in-game reference. The current order is a train wreck and a terrible editorial decision.
Magic is now in softcover. The good news is that you have all the errata included. The bad news is this is precisely the kind of book that you want in hardcover (and color!). If you do get a chance, get the second printing hardcover.
With all that said, this is a must-have supplement for GURPS players using magic in their campaigns.